Kathleen Erin "Kate" Walsh (born October 13, 1967) is an American film and television actress, currently known for her role as Dr. Addison Montgomery on the ABC dramas Grey's Anatomy and Private Practice. Before modelling, Walsh worked at Burger King and Dairy Queen. She began as a model in Japan in the 1980s where she also taught English. Later she moved to Chicago and worked with the Piven Theatre Workshop. She also performed on National Public Radio in the production of the radio play Born Guilty. Walsh later moved to New York City and joined the comedy troupe Burn Manhattan on June 27, 1987, performing in a number of Off-Broadway plays.
After playing Cathy Buxton in the "Stakeout" episode of Homicide: Life on the Street in 1996, her first major television appearance was in 1997, when she appeared on The Drew Carey Show as Carey's character's girlfriend Nicki. She wore a fatsuit in some episodes of the show, as the Nicki character was a formerly obese woman who lost weight and slowly started to gain it back. She went on to portray Carol Nelson in HBO's The Mind of the Married Man television series, and played Norm Macdonald's romantic interest in the sitcom The Norm Show. Walsh also made a guest appearance on CSI: Crime Scene Investigation as Mimosa, a transsexual. She sometimes appeared in sketches on Late Night with Conan O'Brien. She had a recurring role on Karen Sisco as Detective Marley Novak in 2003 and 2004. In 2005, she was cast in the ABC series, Grey's Anatomy, as Dr. Addison Montgomery, the estranged spouse of Derek Shepherd ("Dr. McDreamy", played by Patrick Dempsey).
It was announced in February 2007 that Walsh's Grey's Anatomy character Addison would be in a spin-off of Grey's Anatomy that began airing in September 2007. Taye Diggs, Tim Daly, Amy Brenneman, Chris Lowell and Audra McDonald have been cast in the spin-off, which has been given the name Private Practice. Walsh returned to Seattle Grace as a guest star for episode thirteen in Season 4 and episodes 15 and 16 in Season 5 of Grey's Anatomy. She also briefly returned for an episode of the sixth season of Grey's Anatomy to help Mark Sloan with his newfound daughter, who is pregnant. Later in season 7 she returned to operate on Dr. Callie Torres (Sara Ramirez) because Callie was in a car crash and at this point she was pregnant.
She is currently playing the character of Addison Montgomery in the fourth season of Private Practice, for which ABC has ordered a full season of episodes. On January 10, 2011 ABC picked up "Private Practice" for the 2011-2012 fall season (5th season). Walsh guest-starred in the musical episode of Grey's Anatomy, season 7 episode 18, "Song Beneath The Song".
Beginning in September 2007, Walsh has appeared in television commercials for the 2008 Cadillac CTS. She is also the current spokeswoman for Caress' Exotic Oil Infusions body wash